1. Field of the Invention
The present invention relates to an electronic device, an electronic device control method, and an electronic device control program.
2. Background Art
Small electronic devices such as a timepiece device including a wristwatch which is equipped with a power generating unit such as a solar cell and a secondary power supply have been put to practical use. In the electronic devices, power generated by the power-generating unit is charged to the secondary power supply, and time is displayed by the power supplied from the secondary power supply. As a result, power supply with stabilized output has been realized without replacing the power source.
In the electronic device, if power is kept supplied for a long time from the secondary power supply while the power-generating unit does not generate power, the secondary power supply gets into an overdischarged state in which the charge stored in the secondary power supply becomes zero. In the overdischarged state, even if power starts to be supplied from the power-generating unit, the electronic device cannot be operated until sufficient charge is stored in the secondary power supply.
JP-A-2000-230988 discloses an electronic device in which when a normal operation state is continued for a certain period of time while power is not supplied, the operation state transits to a low power consumption state in which time is not displayed, whereby the power consumption is suppressed.
However, in the invention disclosed in JP-A-2000-230988, there is a case that it is difficult for the power-generating unit to generate power depending on the usage environment, and the operation state transits to the low power consumption state. For example, in a wristwatch to which the invention of JP-A-2000-230988 is applied, when light is blocked since the wristwatch is covered by cuffs, or when the wristwatch is not irradiated with light in the night, power generation is not performed. If the power generation is not performed for a certain period of time, time display is stopped.
Furthermore, the invention disclosed in JP-A-2000-230988 has a drawback that the electronic device is overdischarged depending on the length of time for which the power generation is not performed, and it takes time to resume the operation of the electronic device. For example, after the device is shipped from a factory, if the device is overdischarged since the device has not been irradiated with light for a long time, the time display is not performed until the operation of the device is resumed. This state leads to a concern that a user might misunderstand the device is out of order.
As described above, the invention disclosed in JP-A-2000-230988 has a drawback that there is a case that the user cannot check the time display when he or she wants to check time.